forked from mirror/async-std
58 lines
1.2 KiB
Rust
58 lines
1.2 KiB
Rust
use std::pin::Pin;
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use pin_project_lite::pin_project;
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use crate::stream::Stream;
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use crate::task::{Context, Poll};
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pin_project! {
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/// A stream that will repeatedly yield the same list of elements
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pub struct Cycle<T> {
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source: Vec<T>,
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index: usize,
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len: usize,
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}
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}
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impl<T: Copy> Stream for Cycle<T> {
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type Item = T;
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fn poll_next(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
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let value = self.source[self.index];
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let next = self.index + 1;
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self.as_mut().index = next % self.len;
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Poll::Ready(Some(value))
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}
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}
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/// # Examples
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///
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/// Basic usage:
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///
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/// ```
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/// # async_std::task::block_on(async {
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/// #
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/// use async_std::prelude::*;
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/// use async_std::stream;
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///
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/// let mut s = stream::cycle(vec![1,2,3]);
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///
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/// assert_eq!(s.next().await, Some(1));
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/// assert_eq!(s.next().await, Some(2));
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/// assert_eq!(s.next().await, Some(3));
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/// assert_eq!(s.next().await, Some(1));
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/// assert_eq!(s.next().await, Some(2));
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/// #
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/// # })
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/// ```
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pub fn cycle<T: Copy>(source: Vec<T>) -> impl Stream<Item = T> {
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let len = source.len();
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Cycle {
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source,
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index: 0,
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len,
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}
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}
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